Cavity Micro Electrodes (C-MEs) & SECM (Scanning ElectroChemical Microscopy) for the Investigation of Photoactive Semiconductor Materials and the Evaluation of Photodegradation Process during PEC_WS

Photoelectrochemical water splitting using semiconducting materials is an interesting route to produce hydrogen (or other chemicals, e.g. oxygen) using solar energy. However, these materials might exhibit poor stability under photoexcitation and degrade in aqueous solution leading to a progressive loss of efficiency. Our work aimed to set up and validate a simple and fast method for screening libraries of materials and identifying their efficiency in H2 (or O2) production respect to side reactions or photocorrosion. The proposed method is applicable to any semiconductor powder for a fast, preliminary evaluation of the material, in the absence of any effect of the supporting material (i.e. the current collector, FTO). Here, scanning electrochemical microscopy (SECM) in tip generation /substrate collection (TG/SC) [1] mode in combination with cavity microelectrodes [2-3] were used to characterize the behaviour of different powder materials: CuO/Cu2O coreshell NP [4], NiO, CuI and TiO2. The preliminary feasibility was confirmed by the use of Pt/Vulcan XC-72 (28.6% w/w) powder as standard material. The influence of different wavelength light on the whole system was evaluated too [5]. References [1] S. Morandi, A. Minguzzi Electrochemistry Communications, 59, (2015) 100–103. [2] A. Minguzzi, C. Locatelli, O. Lugaresi, A. Vertova, S. Rondinini, Electrochimica Acta 114, (2013), 637-642. [3] C. Locatelli, A. Minguzzi, A. Vertova, P. Cava, S. Rondinini, Analytical Chemistry, 83, 7, (2011) 2819-2823. [4] T. Baran, A. Visibile, S. Wojtyła, M. Scavini, F. Malara, A. Naldoni, A. Minguzzi, Reverse Type I core/shell CuxO@CuI: versatile heterostructure for photoelectrochemical applications (in preparation). [5] V. V. Yakushev, A. M. Skundin, V. S. Bagotskii, Electrokhimiya, 20, (1982), 99-104.